linux-kernel - Re: [PATCH v6 1/3] phy: core: Reword the comment specifying the units of max_link

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Date:   Fri, 11 Jun 2021 18:31:54 +0530
From:   Kishon Vijay Abraham I <kishon@...com>
To:     Aswath Govindraju <a-govindraju@...com>,
        Vinod Koul <vkoul@...nel.org>
CC:     <linux-can@...r.kernel.org>,
        Marc Kleine-Budde <mkl@...gutronix.de>,
        Wolfgang Grandegger <wg@...ndegger.com>,
        Vignesh Raghavendra <vigneshr@...com>,
        Lokesh Vutla <lokeshvutla@...com>,
        Rob Herring <robh+dt@...nel.org>,
        <linux-phy@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 1/3] phy: core: Reword the comment specifying the units
 of max_link_rate to be Mbps

Hi,

On 11/06/21 6:12 pm, Aswath Govindraju wrote:
> Hi Vinod,
> 
> On 31/05/21 2:04 pm, Aswath Govindraju wrote:
>> Hi Vinod,
>>
>> On 31/05/21 12:48 pm, Vinod Koul wrote:
>>> On 10-05-21, 10:40, Aswath Govindraju wrote:
>>>> In some subsystems (eg. CAN, SPI), the max link rate supported can be less
>>>> than 1 Mbps and if the unit for max_link_rate is Mbps then it can't be
>>>> used. Therefore, leave the decision of units to be used, to the producer
>>>> and consumer.
>>>>
>>>> Signed-off-by: Aswath Govindraju <a-govindraju@...com>
>>>> Acked-by: Marc Kleine-Budde <mkl@...gutronix.de>
>>>> ---
>>>>  include/linux/phy/phy.h | 2 +-
>>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>>
>>>> diff --git a/include/linux/phy/phy.h b/include/linux/phy/phy.h
>>>> index 0ed434d02196..f3286f4cd306 100644
>>>> --- a/include/linux/phy/phy.h
>>>> +++ b/include/linux/phy/phy.h
>>>> @@ -125,7 +125,7 @@ struct phy_ops {
>>>>  /**
>>>>   * struct phy_attrs - represents phy attributes
>>>>   * @bus_width: Data path width implemented by PHY
>>>> - * @max_link_rate: Maximum link rate supported by PHY (in Mbps)
>>>> + * @max_link_rate: Maximum link rate supported by PHY (units to be decided by producer and consumer)
>>>
>>> So there are a few users of max_link_rate. It would be better that we
>>> document all previous users of max_link_rate that unit is in Mbps and
>>> then modify it here
>>>
>>
>> I was able to see that the max_link_rate attribute was used at,
>>
>> drivers/phy/cadence/phy-cadence-torrent.c:2514:
>> gphy->attrs.max_link_rate = cdns_phy->max_bit_rate;
>>
>> and in the bindings there is indication that the units to be used is Mbps.
>>
>> Can you please point me if there is any other place that I might have
>> missed to look at or that might need documentation update?
>>

The only user seems to be Torrent and max_bit_rate is documented well in
Torrent.

Acked-by: Kishon Vijay Abraham I <kishon@...com>

Thanks
Kishon